1. Field of the Invention
This invention relates to electrostatic recording apparatus of the duplex control type, for passing a recording medium between recording electrodes and complementary electrodes for electrically charging selected regions of a dielectric layer of the recording medium, and more particularly to a novel recording medium of such apparatus.
2. Description of the Prior Art
Heretofore, in this electrostatic recording apparatus, it has been customary to arrange recording electrodes N of the pin electrode type in arrays of n in number (n is a positive integer), and complementary electrodes G disposed adjacent the recording electrodes N are also arranged as complementary electrodes G.sub.1, G.sub.2. . . G.sub.2 which are respectively juxtaposed against the corresponding arrays of recording electrodes N as shown in FIG. 1. Electrodes of an ordinal number j (j = 1, 2, 3 . . . m) of all the arrays of recording electrodes N are connected to switches Z.sub.j of an ordinal number j. In operation of the switches Z and one of switches K.sub.1, K.sub.2 . . . K.sub.n of the complementary electrodes G are selectively opened and closed. For example, if switches Z.sub.1 and K.sub.2 are selected, then an electric field of strength sufficiently high to produce a discharge is created between the electrodes (electrodes N.sub.21 and G.sub.2) to which voltages are simultaneously applied through the two switches and a discharge takes place therebetween. The art of applying a voltage or impulse to the recording medium from both sides thereof in this way for simplifying selective control of the recording electrodes N in the form of pin electrodes is known from Japanese Patent Publication No. 24642/73, for example.
Generally, the recording medium 1 may be formed by providing a conductive layer on one side or on both sides of a base which may be paper, and by providing a dielectric layer thereon by applying silicone resin, vinyl acetate resin, vinyl chloride resin, etc. Alternatively, a base formed of paper or an insulating resin plate may be made to contain minuscle particles of metal, a surface activator, or other conductive material so as to render the base itself electrically conductive. A dielectric layer may then be formed on the base functioning coextensive with the conductive layer. The recording medium shown in FIG. 1 includes a conductive support 2 formed by applying an electrically conductive material to paper or other suitable support material or impregnating such support material with an electrically conductive material, and a dielectric layer 3 formed on the conductive support. Thus is switches K.sub.1 and Z.sub.1 are selected, for example, then a discharge will occur between the electrodes N.sub.11 and G.sub.1 as desired, but a discharge of less intensity will also occur between an electrode N.sub.21 of the adjacent array of recording electrodes and the complementary electrode G.sub.1. This will cause a portion of the dielectric layer of the recording medium which is disposed beneath the recording electrode N.sub.21 to be charged, with the result that what is referred to as a ghost image will be produced in the recorded likeness of the original. To obviate this defect, proposals have been made to provide improvements in the arrangement of electrodes or in control systems. However, there has hitherto been no satisfactory solution proposed to solve this problem. A difficulty has been experienced in the proir art particularly when an attempt is made to carry out recording in an atmosphere of high humidity.